The present invention relates generally to a device for detecting the angular position of a rotating part, and more particularly to a device incorporating a timing ring for detecting the angular position of a shaft of an internal combustion engine.
It is known to sense the rotational position and/or speed of a shaft, for example a crankshaft in an internal combustion engine, by means of a timing ring which rotates with the shaft, a perimeter of the timing ring comprising teeth which each create an impulse as they pass an electrical sensor. The sensor output is an essential element of engine management systems. It is also known for the timing ring to be additionally provided with a variation in the teeth at one or more points so that the sensor can detect the rotational position (angle) of the shaft at a precise instant in time. Examples of such known timing rings may be seen in U.S. Pat. No. 4,233,592, U.S. Pat. No. 4,742,332 and U.S. Pat. No. 5,497,748.
However, in an internal combustion engine, auxiliary drives taken from the front end of the crankshaft and transmissions or generators driven from the rear end limit the space available for installing the timing ring and its associated sensor.
Further, even where space can be allocated for the timing ring and sensor, it can be difficult to gain access to retain a crankshaft driven timing ring with threaded fasteners or the like, and the process can be time consuming and costly both in component manufacture and in subsequent fitment to the engine. However, non-permanent fastening, for instance with threaded fasteners, may be necessary in conventional apparatus to allow the timing ring to be removed for certain aspects of engine servicing or for replacement of the timing ring, for example after accidental damage to the timing ring teeth.
A further problem may arise in attempting to fit a timing ring to an engine in a location offering protection to the teeth from accidental damage, which could result in incorrect rotational sensing, and ensuring that the rotating timing ring will not pose a danger to engine operators or other personnel who may venture into the vicinity when the engine is in operation. These problems may be overcome by enclosing the timing ring in a dedicated enclosure, but this will increase the manufacturing cost of the engine and may also be physically difficult to incorporate into the engine.
A known alternative or addition to driving the timing ring directly from the crankshaft is to rotatingly drive it from a camshaft. U.S. Pat. No. 5,460,134 shows a system where timing rings (discs) are driven from both crankshaft and camshaft. A timing ring driven by a camshaft provides the benefit, in a four-stroke engine, of the timing ring turning one complete revolution per 720xc2x0 of crankshaft rotation. Thus a single marker tooth can uniquely signify each repeat of an in-cylinder combustion event since these events occur every 720xc2x0 of crankshaft revolution. Conversely, a crankshaft-driven timing ring cannot distinguish between the different events that occur alternatingly every 360xc2x0 degrees of crankshaft rotation. However, installation, access and other problems similar to those related above in relation to crankshaft-driven timing rings may also be experienced with camshaft-driven timing rings.
It is desirable to provide a timing ring apparatus and method of assembly to an engine which will obviate or mitigate the problems identified above.
The present invention is directed to overcoming one or more of the problems as set forth above.
In one aspect of the present invention there is provided a timing apparatus having a gear and a timing ring. The gear has a first face, a second face, an outer toothed portion having a first width and an inner web portion having a second width and the gear having a generally cylindrical recess on the first face of the gear. The timing ring is secured within the recess.
in another aspect of the present invention, a timing apparatus has a gear having gear teeth and a first face. A timing ring is located on the first face of the gear and has a plurality of circumferentially spaced timing teeth adapted to provide rotational and/or positional data to a timing sensor. The timing teeth are arranged radially inwardly of the gear teeth.
In yet another aspect of the present invention, a timing apparatus has a gear having a first face, a second face, an outer toothed portion having a first width, an inner web portion having a second width less than the first width. A generally cylindrical recess is disposed on the first face of the gear. A timing ring is disposed within the recess and connected to the gear.